It's extremely unlikely for people to actually get stuck or die in quicksand. In real quicksand with flowing water, you would float once enough of you was in it. The problem comes when you are in the quicksand and the water stops flowing causing the sand to solidify and trap you there or possibly mechanically asphyxiate you from the pressure of the sand on your body.

However, that condition mostly happens in man made quicksand demonstrations for TV, not in reality.